South America: where to buy a car and register (so exporting it is possible)

Dear Traveler :)

I'm struggling with overworried parents of my GF, so I have to didge my motorcycle and get a car :-/ once she joins me in Colombia/Ecuador/Venezuela

1. is there any known problem with travelling with a car through the countries of South America? (I know, with a bike they let you, but not sure about temporary import documents?)

2. Where is it recommendable to buy a car?? (Colombia/Venezuela/Ecuador would be preferable, because I could ship the bike from Panama to Europe and get a car after crossing the Panama Canal, but I could also fly to every country down there, chosing a different route to connect the rest of South America)
--> one aspect is to get a cheap offer for a 4x4 used car, that has space for a matress in back
--> other aspect: where can I get it registered and TAKE IT OUT of the country? (I heard, could be a problem)

3. I have two places to ask for international insurance, but I'm still open for recommendations (cheap and/or good coverage)

I really, really appreciate all your help! ..I'm a 28 year old guy from Switzerland, that is on the trip of his life from Alaska to Ushuaia on a BMW 650 GS Dakar and I met the girl of my life! :) ..one part of the compromise with her parents is to make Central America alone (because apparently too dangerous :P) and to ride a car, not a bike.. lot's of circumstances, but hell.. there must be a way!

so thank you for helping me out with these special requests! :)

happy trails and good speed to all of you!

Markus